1. Field of the Invention
The present invention is in the field of liquid phase epitaxy method for the manufacture of three-dimensional semiconductor structures on silicon substrates which are provided with insulation layers, utilizing a metal melt as a solvent for epitaxially depositing uniformly doped silicon layers and manufacturing semiconductor structures in these layers.
2. Description of the Prior Art
In microelectronics, it is necessary for three-dimensional integration of component structures to apply a plurality of silicon layers on top of one another in an insulated fashion. Active and passive components such as, for example, thin film transistors, bi-polar transistors, and capacitors are then generated in these layers with the method steps which are standard in microelectronics.
The typical means for generating silicon layers on silicon dioxide layers has been deposition from the vapor phase. These layers are initially polycrystalline. These polycrystalline layers can be melted with lasers, graphite heaters, or intense radiation sources, and can then be recrystallized into single crystal layers proceeding from a window in the oxide layer. The single substrate in the window thereby acts as a seed and determines the orientation of the single cystal layer by the process of lateral seeding. A disadvantage of this method is that the silicon substrate is necessarily heated in the recrystallization range and the components which are already manufactured can suffer thermal damage. This type of method is disclosed, for example, in European Patent Application No. 0 117 339.
In DE-AS No. 24 45 146 there is disclosed the deposition of thin, doped single crystal layers by means of liquid phase epitaxy. The substrate to be coated is brought into contact by centrifugal force with a metal melt containing the layer material. The metals gallium, bismuth, indium, antimony, and tin are employed as solvents for the silicon.
In an article by Kass et al. appearing at the ESSDERC, 1985, it is shown that layers laterally grown over SiO.sub.2 can be produced with uniform doping. As described in European Patent Application No. 0117339, such silicon layers manufactured by liquid phase epitaxy can be employed for the manufacture of three-dimensional component structures. Gallium is preferably employed for the liquid phase epitaxy as a solvent for the silicon in this patent application, as well as in the periodical "Physica", vol. 129B (1985), pages 161-165. This combination produces a concentration of doping which is greater than 10.sup.18 /cm.sup.3 and is therefore not suitable as a basic doping for the three-dimensionally constructed layers of an integrated semiconductor circuit.